Input protection circuitry is an important area of electronic technology. Extremely small delicate device structures are very sensitive to high voltages which may be developed by an electrostatic discharge ("ESD") from a human body. When an electronic circuit is installed into a part, such an electrostatic discharge may destroy the part or reduce the part's quality or capacity. For example, an electrostatic discharge may develop an extremely high voltage which quickly destroys the thin gate oxides and short channel devices of high density complimentary metal oxide semiconductor ("CMOS") field effect transistor circuits.
Previous techniques have been developed for dissipating electrostatic discharges in order to avoid such negative effects. However, typical previous techniques have very high threshold trigger voltages. A high threshold trigger voltage is frequently insufficient to adequately protect certain devices on the electronic circuit, such as an n-channel field effect transistor. Some previous techniques for lowering threshold trigger voltages nevertheless present alternative problems, such as occupation of a large amount of semiconductor fabrication area.
Thus, a need has arisen for circuitry and structures for electrostatic discharge protection, which have low threshold trigger voltages. Also, a need has arisen for circuitry and structures for electrostatic discharge protection, which protect field effect transistors. Moreover, a need has arisen for circuitry and structures for electrostatic discharge protection, which occupy a small amount of semiconductor fabrication area.